Portable inhalers include pMDIs, DPIs and portable nebulizers. They are used to deliver medicinal substance to the lungs, to the nasal passages, to the buccal cavity or sublingually.
pMDIs are well known in the art of inhalation devices. It is therefore not necessary to describe the construction and operation of a pMDI other than in bare essentials.
A pMDI typically comprises a canister and an actuator. The actuator typically includes a tubular housing provided with a patient port, for example a mouthpiece or a nosepiece. The housing is generally formed of a plastics material, for instance by molding (e.g. plastic injection molding). Typical plastics used for actuators are high density polyethylene, polypropylene or poly-acrylonitrile-butadiene-styrene. The canister comprises an open-ended container (typically made from a metal such as aluminum) capped by a metering valve and filled with medicinal aerosol formulation. It is inserted valve-down into the top of the tubular housing so that an outlet stem of the valve engages a nozzle block of the actuator located near the patient port.
In use, a patient in need of a metered dose of the medicinal aerosol formulation concurrently inhales through the patient port and depresses the base of the canister to move the canister from the rest position to the actuated position. The metered dose of the medicinal aerosol formulation is either entrained by the patient's inspiratory airflow into the patient's respiratory tract or nasal passages, or the metered dose of spray impacts directly onto the target organ.
Inhalers are commonly provided with a dust cap, made of the same material as the actuator, which covers the patient port when the inhaler is not in use. The dust cap, when applied, prevents foreign material from entering the housing. This prevents the user from inhaling for example, dust or lint, which might otherwise accumulate in the housing. This is of particular importance where the user suffers from asthma or other respiratory conditions, in which the inhalation of foreign material may cause severe irritation.
However, the dust cap is often lost by the patient, in which circumstance so also is its benefit in respect of subsequent doses to be taken.
Consequently, some inhalers, particularly pMDIs provided for the US market are provided with caps that are attached to actuators by some means.
WO-A-2002/04056 describes embodiments in which the cap is connected to the housing by a strap formed of a thermoplastic elastomer material. The strap is joined to the cap and housing by mechanical fasteners, glue, heated or ultrasonic welds or a combination of these means.
WO-A-2005/046774 discloses an inhaler in which the cap is attached to the actuator by means of a strap. The cap is arranged to slide on the strap, which is co-molded with the actuator.
WO-A-2005/087299 discloses an inhaler in which the cap is attached to the actuator by means of a telescopic strap. The telescopic strap consists of two components; a first component is attached to the cap by a hinge, e.g. a “living hinge”, and the second component is attached to the actuator in the same way but optionally also with a hole that fits over a stud on the actuator.